Safety-guard detective circuit of a fan motor

ABSTRACT

A safety-guard detective circuit of a fan motor includes a resistor being adapted to limit a large current input into the motor driver circuit, and a discharge member being adapted to perform grounding to discharge the large current limited by the resistor. The resistor and the release member are commonly connected to the third lead of the motor driver circuit.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a safety-guard detective circuitof a fan motor, and more particularly to the safety-guard detectivecircuit is connected to a rotation detective terminal of a third lead ofthe fan motor and thus the fan motor has a rotation detective circuitwhich can avoid the motor driver IC inputting discharge breakdown andwire short.

[0003] 2. Description of the Related Art

[0004]FIG. 1 is a circuit diagram of a conventional driver circuit and aconventional rotation detective circuit (phantom lines) of a dcbrushless motor.

[0005] As shown in FIG. 1, the conventional motor driver circuit 1includes a driver IC, and two coils L1 and L2. A hall bolt module and acontrol module (transistor) are built in the driver IC. A hall memberbeing adapted to detect change of the magnetic field of the permanentmagnet of the rotor, and the weak hall voltage is amplified by thedriver IC. The two output terminals OUT1 and OUT2 of the driver IC thenalternatively outputs current to the two coils L1 and L2 so the twocoils L1 and L2 are excited to rotate the rotor. In this time, the twooutput terminals OUT1 and OUT2 of the driver IC simultaneously outputtwo opposite phase square waves. The conventional rotation detectivecircuit 10 generally includes a transistor Q1, and a resistor R1 todefine an amplifier circuit. The resistor R1 is connected in series thebase of the transistor Q1 with the output terminal OUT2 while thecollector of the transistor Q1 is predetermined as a rotation detectiveterminal, as well as a third lead.

[0006]FIG. 2 is a circuit diagram of a conventional driver circuit and arotation detective terminal of a single phase dc brushless motor. Asshown in FIG. 2, the conventional motor driver circuit 1 includes a hallsensor IC1 and a driver IC2. The output terminal of the hall sensor IC1is connected to the input terminal of the driver IC2. The two outputterminals of the driver IC2 are connected to a coil L1 An outputterminal FG of the driver IC2 is predetermined as a rotation detectiveterminal, as well as a third lead.

[0007] In application of the motor driver circuit, the third lead of thedriver circuit of the dc brushless motor, as shown in FIGS. 1 and 2, isprovided for connecting to a rotation detective circuit. In general, thethird lead is reserved and exposed to thereby facilitate assemblyoperation of the motor. However, during assembly operation the thirdlead may possibly contacted with human body. Discharge breakdown willoccur through the third lead as the human body has considerableelectricity. Thus the driver IC or the transistor of the motor will bedamaged by the static electricity. Referring again to FIG. 1, duringassembly operation if the third lead is connected to a power source, alarge current is directly input into the base of the transistor Q1 orthe driver IC that must damage the transistor or results in wire shortof the driver IC. To avoid the occurrence of transistor damage anddriver IC's wire short during the assembly operation, a need exists forthe third lead with a safety-guard device, thereby enhancing thereliability of the motor function.

SUMMARY OF THE INVENTION

[0008] Accordingly, the present invention may improve theabove-mentioned drawbacks, wherein a third lead, as well as a rotationdetective terminate, of the motor driver is connected with asafety-guard detective circuit. Thus, when the human body contacts withthe third lead during assembly operation of the motor, the safety-guarddetective circuit is adapted to limit a large current inputting into themotor driver through the third lead. And a discharge member, a zenerdiode for example, is adapted to grounding the large current to therebyavoid transistor damage and driver IC's wire short.

[0009] The primary objective of the present invention is to provide asafety-guard detective circuit of a fan motor, wherein the motor driveris connected with a safety-guard detective circuit which is adapted tolimit a large current inputting into the motor driver through the thirdlead when the human body contacts with the third lead during assemblyoperation of the motor, to thereby avoid transistor damage and driverIC's wire short.

[0010] In accordance with the present invention, a safety-guarddetective circuit of a fan motor includes a resistor limiting a largecurrent inputting into a motor driver circuit, and a discharge membergrounding the large current limited by the resistor. The resistor andthe discharge member are commonly connected to a third lead of the motordriver circuit.

[0011] Further benefits and advantages of the present invention willbecome apparent after a careful reading of the detailed description withappropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a circuit diagram of a conventional driver circuit and aconventional rotation detective circuit of a double phase dc brushlessmotor;

[0013]FIG. 2 is a circuit diagram of a conventional driver circuit and a

[0014] rotation detective terminal of a single phase dc brushless motor;

[0015]FIG. 3 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a driver circuit of a double phase dc brushless motor inaccordance with a first embodiment of the present invention;

[0016]FIG. 4 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a driver circuit of a double phase dc brushless motor inaccordance with a second embodiment of the present invention;

[0017]FIG. 5 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a drive circuit of a double phase dc brushless motor inaccordance with a third embodiment of the present invention;

[0018]FIG. 6 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a drive circuit of a double phase dc brushless motor inaccordance with a fourth embodiment of the present invention;

[0019]FIG. 7 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a drive circuit of a single phase dc brushless motor inaccordance with a fifth embodiment of the present invention;

[0020]FIG. 8 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a drive circuit of a single phase dc brushless motor inaccordance with a sixth embodiment of the present invention; and

[0021]FIG. 9 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a drive circuit of a single phase dc brushless motor inaccordance with a seventh embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The safety-guard detective circuit of a fan motor in accordancewith the present invention includes a resistor and a discharge memberwhich are commonly connected to the third lead of the motor drivercircuit. The resistor is used to limit a large current inputting intothe motor driver circuit, and the discharge member, a zener diode forexample, is used to ground to the large current limited by the resistor.The safety-guard detective circuit of a fan motor in accordance with thepresent invention may be applied in a double phase dc brushless motor inaccordance with the first, second, third and fourth embodiments of thepresent invention. At the same time, the safety-guard detective circuitof a fan motor in accordance with the present invention may be appliedin a single phase dc brushless motor in accordance with the fifth, sixthand seventh embodiments of the present invention.

[0023] Some of the parts of the double phase dc brushless motor inaccordance with the first, second, third and fourth embodiments of thepresent invention are the same as those of the conventional double phasedc brushless motor. The same parts of these embodiments will be adaptedthe same reference numerals for clarity. In addition, the same parts ofthe first, second, third and fourth embodiments of the present inventionhave the similar configuration and same functions as those of theconventional double phase dc brushless motor, and detailed descriptionsthereof are omitted.

[0024]FIG. 3 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a drive circuit of a two-phase direct current brushlessmotor in accordance with a first embodiment of the present invention.

[0025] Referring to FIG. 3, the safety-guard detective circuit 10 of afan motor comprises a first resistor R1, a second resistor R2, a thirdresistor R3, a transistor Q1, and a discharge member Z1. Thesafety-guard detective circuit 10 is connected to a output terminal, aswell as third lead, of the driver IC2 of the motor driver circuit 1, tothereby limit a large current inputting into the output terminal, so asto protect the driver IC2. The safety-guard detective circuit 10 isadapted a fixed bias voltage manner whose fixed bias voltage is providedby the first resistor R1 and the second resistor R2 and used to open orcutoff the base of the transistor Q1. After the voltage of the squarewave signal output from the driver IC2 is divided by the first resistorR1 and the second resistor R2, the divided square wave signal is inputinto the base of the transistor Q1 for being amplified. The square wavesignal as well as a rotation detective signal is amplified, so that thetransistor Q1 is absolutely controlled in saturation or cutoff state.The resistance ratio of the first resistor R1 and the second resistor R2can be adjusted according to the features of the motor driver circuit 1,so the rotation detective circuit may have the optimum detective effect.

[0026] Again referring to FIG. 3, when the motor is driven, the driverIC2 of the motor driver circuit 1 outputs a voltage signal. After thevoltage signal is divided by the first resistor R1 and the secondresistor R2, the divided signal is input into the base of the transistorQ1 that absolutely controls the transistor Q in saturation or cutoffstate.

[0027] Again referring to FIG. 3, the third resistor R3 is connected inseries to the collector of the transistor Q1, which limits either anydischarge breakdown or large current inputting into the collector due towire short. At the same time, a discharge member Z1 is connected thebase of the transistor Q1 to ground to thereby form a discharge passagebetween the base of the transistor Q1 and the ground. Consequently, thethird resistor R3 limits a large current discharged from this dischargepassage. Preferably, the discharge member Z1 is a zener diode. Thus,during assembling the motor, as human body is in contact with the thirdlead, the safety-guard detective circuit 10 may limit the large currentthrough the third lead to input into the driver IC2 of the motor drivercircuit 1. Meanwhile, the discharge member Z1 grounds this largecurrent, thereby avoiding the driver IC2 being damaged by dischargebreakdown and wire short.

[0028] Again referring to FIG. 3, the third resistor R3 is connected inseries to the collector of the transistor Q1. Thus, during actuating thetransistor Q1, the voltage of the output logic low level is increased.In normal application, the signal current input into the collector ofthe transistor Q1 is usually smaller than 10 mA. If the resistance ofthe third resistor R3 is limited smaller than 50Ω, the current 10 mA isdropped slightly smaller than 0.5V by the resistance 50Ω. The totalvalue of the voltage drop 0.5V and the saturation voltage about 0.2V ofthe transistor Q1 is smaller than 0.7V so set that the output stillsatisfies the specification of logic low level. Thus, the transistor Q1of the safety-guard detective circuit 10 efficiently limits the inputcurrent into its collector and may also avoid discharge breakdown input.At the same time, the safety-guard detective circuit 10 may provide thesafe and stable signal detective function of the third lead.

[0029]FIG. 4 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a driver circuit of a double phase dc brushless motor inaccordance with a second embodiment of the present invention. FIG. 5 isa circuit diagram of a safety-guard detective circuit of a fan motor anda driver circuit of a double phase dc brushless motor in accordance witha third embodiment of the present invention. FIG. 6 is a circuit diagramof a safety-guard detective circuit of a fan motor and a driver circuitof a double phase dc brushless motor in accordance with a fourthembodiment of the present invention.

[0030] Some of the parts of the safety-guard detective circuit inaccordance with the second, third and fourth embodiments of the presentinvention are the same as that of the safety-guard detective circuit ofthe first embodiment. The same parts of these embodiments will beadapted the same reference numerals for clarity. In addition, the sameparts of the second, third and fourth embodiments of the presentinvention have the similar configuration and same functions as those ofthe first embodiment, and detailed descriptions thereof are omitted.

[0031] Referring to FIG. 4, the safety-guard detective circuit 10 of afan motor and a driver circuit of a double phase dc brushless motor inaccordance with a second embodiment of the present invention comprises aresistor R1, and a discharge member (such as zener diode) Z1. Thesafety-guard detective circuit 10 is connected to the output terminalFG/RD (such as the third lead) of the driver IC2, so as to avoid thisoutput terminal FG/RD being input by a large current. The resistor R1 isconnected in series to the output terminal FG/RD of the driver IC2, sothat the voltage of the output logic low level is increased. In a normalapplication, the output signal current of the driver IC2 is usuallysmaller than 10 mA. If the resistance of the resistor R1 is limited tobe smaller than 50Ω, the current of 10 mA is dropped slightly smallerthan 0.5V by the resistance of 50Ω. The total value of the voltage drop0.5V and the saturation voltage about 0.2V of the output terminal FG/RDis smaller than 0.7V, so set that the output still satisfies the logiclow level which thereby performs as the detective signal of the thirdlead.

[0032] Referring to FIG. 5, the safety-guard detective circuit 10 of afan motor and a driver circuit of a double phase dc brushless motor inaccordance with a third embodiment of the present invention comprises afirst resistor R1, a second resistor R2, a third resistor R3, atransistor Q1, and a discharge member (such as zener diode) Z1. Thesafety-guard detective circuit 10 is connected to the collector of thetransistor Q3, thereby avoiding a large current inputting into theoutput terminal of the motor driver circuit 1.

[0033] Referring to FIG. 6, the safety-guard detective circuit 10 of afan motor and a drive circuit of a two-phase dc brushless motor inaccordance with a fourth embodiment of the present invention comprises afirst resistor R1, a second resistor R2, a third resistor R3, atransistor Q1, and a discharge member (such as zener diode) Z1. Thesafety-guard detective circuit 10 is connected to the output terminal ofthe hall member IC1, thereby avoiding a large current inputting into theoutput terminal of the motor drive circuit 1.

[0034]FIG. 7 is a circuit diagram of a safety-guard detective circuit ofa fan motor and a driver circuit of a single phase dc brushless motor inaccordance with a fifth embodiment of the present invention. FIG. 8 is acircuit diagram of a safety-guard detective circuit of a fan motor and adriver circuit of a single phase dc brushless motor in accordance with asixth embodiment of the present invention. FIG. 9 is a circuit diagramof a safety-guard detective circuit of a fan motor and a driver circuitof a single phase dc brushless motor in accordance with a seventhembodiment of the present invention.

[0035] Some of the parts of the single phase dc brushless motor inaccordance with the fifth, sixth and seventh embodiments of the presentinvention are the same as those of the conventional single phase dcbrushless motor. The same parts of these embodiments will be adapted thesame reference numerals for clarity. In addition, the same parts of thefifth, sixth and seventh embodiments of the present invention have thesimilar configuration and same functions as those of the conventionalsingle phase dc brushless motor, and detailed descriptions thereof areomitted.

[0036] Referring to FIG. 7, the safety-guard detective circuit 10 of afan motor and a driver circuit of a single phase dc brushless motor inaccordance with a fifth embodiment of the present invention comprises afirst resistor R1, a second resistor R2, a third resistor R3, atransistor Q1, and a discharge member (such as zener diode) Z1. Thesafety-guard detective circuit 10 is connected to the output terminal(such as the third lead) of the driver IC2, thereby avoiding a largecurrent inputting into the output terminal of the driver IC2.

[0037] Referring to FIG. 8, the safety-guard detective circuit 10 of afan motor and a drive circuit of a single phase dc brushless motor inaccordance with a sixth embodiment of the present invention comprises aresistor R1, and a release member (such as zener diode) Z1. Thesafety-guard detective circuit 10 is connected to the output terminalFG/RD (such as the third lead) of the driver IC2, thereby avoiding alarge current inputting into the output terminal FG/RD of the driverIC2.

[0038] Referring to FIG. 9, the safety-guard detective circuit 10 of afan motor and a driver circuit of a single phase dc brushless motor inaccordance with a seventh embodiment of the present invention comprisesa first resistor R1, a second resistor R2, a third resistor R3, atransistor Q1, and a discharge member (such as zener diode) Z1. Thesafety-guard detective circuit 10 is connected to the output terminal ofthe hall member IC1, thereby avoiding a large current being input intothe output terminal of the hall member IC1.

[0039] Again referring to FIGS. 1 and 2, the conventional rotationdetective circuit 10 of a dc brushless motor only includes a transistorQ1, and a resistor R1 to function as an amplification circuit. Thus,during assembling the motor, the conventional rotation speed detectivecircuit 10 may be damaged by discharge breakdown and wire short.

[0040] Again referring to FIGS. 3-9, in comparison with the presentinvention and the conventional rotation detective circuit as shown inFIGS. 1 and 2, the safety-guard detective circuit 10 of a fan motor inaccordance with the present invention at least comprises a resistor anda discharge member which are commonly connected to the third lead of themotor driver circuit 1. Thus, the resistor is adapted to avoid any largecurrent inputting into the motor driver circuit, and the dischargemember to perform grounding to which discharge the large current limitedby the resistor. In addition, the present invention has the effect ofavoiding discharge breakdown and wire short.

[0041] Although the invention has been explained in relation to itspreferred embodiment as mentioned above, it is to be understood thatmany other possible modifications and variations can be made withoutdeparting from the scope of the present invention. It is, therefore,contemplated that the appended claim or claims will cover suchmodifications and variations that fall within the true scope of theinvention.

What is claimed is:
 1. A safety-guard detective circuit of a fan motorapplied in a driver circuit of a dc brushless motor comprising: aresistor being adapted to limit a large current inputting into the motordriver circuit; and a discharge member being adapted to performgrounding to discharge the large current limited by the resistor;wherein the motor driver circuit is protected by the safety-guarddetective circuit, thereby avoiding the motor driver circuit being inputby the large current.
 2. The safety-guard detective circuit of a fanmotor as claimed in claim 1, wherein the safety-guard detective circuitis applied to a double phase dc brushless motor.
 3. The safety-guarddetective circuit of a fan motor as claimed in claim 1, wherein thesafety-guard detective circuit is applied to a single phase dc brushlessmotor.
 4. The safety-guard detective circuit of a fan motor as claimedin claim 1, wherein the discharge member is a zener diode.
 5. Thesafety-guard detective circuit of a fan motor as claimed in claim 1,further includes a voltage drop circuit and a transistor, and thevoltage drop circuit is connected to a base of the transistor.
 6. Thesafety-guard detective circuit of a fan motor as claimed in claim 5,wherein the voltage drop circuit consists of two resistors.
 7. Thesafety-guard detective circuit of a fan motor as claimed in claim 5,wherein the safety-guard detective circuit is connected to the outputterminal of the driver IC.
 8. The safety-guard detective circuit of afan motor as claimed in claim 5, wherein the safety-guard detectivecircuit is connected to a collector of the transistor.
 9. Thesafety-guard detective circuit of a fan motor as claimed in claim 5,wherein the safety-guard detective circuit is connected to the outputterminal of the hall member IC.